Navaids and Points The purpose of this presentation is to provide an overview of the Aeronautical Conceptual Model for Navaids and Points.

Significant Point A significant point is defined by ICAO as "a specified geographical location used to define an ATS route, the flight path of an aircraft or for other navigation/ATS purposes". A "significant point" is a choice between a navaid, an Airport Reference Point, a runway threshold, a Thouch Down Lift Off, just a latitude and longitude or a designated point. A DesignatedPoint is a named geographical location not marked by the site of a radio navigation aid, used in defining an ATS route, the flight path of an aircraft or for other navigation or ATS purposes.

NavaidEquipment NavaidEquipment has operational hours indicated by the the relationship “workingBy”. The relationship “unmonitoredBy” gives the hours the equipment is not monitored. Navaid Equipment is an abstract feature and is not implemented in the XML schema (XSD). The schema will include the specialization features. The specialization features such as VOR will inherit the attributes and relationships of the generalization class; NavaidEquipment.

Navaid System/Service This diagram shows the separation between the physical equipment and the Navigational System/Service. For example, an ILS is an Instrument Landing System composed of several pieces of equipment that together provides a vertical and lateral guidance service. The ILS can consist of a localizer, a glideslope antenna, distance measuring equipment and markers. NavaidComponent provides the use of the navaid equipment within the navaid system/service. collocationGroup indicates Set of navaid equipment that are collocated. All Navaid equipment that has the same value for this property are collocated together. For example an ILS might have a Glidepath with collocation Group number = 1 and collocated DME and localizer sharing collocationGroup number = 2. markerPostion indicates the position of the markers situated on the centerline of a runway. For example: outer, middle, etc.. The last element indicates the navaid equipment used to specify the navigable location of the Navaid when the navaid is used as significant point.

Service Volumes The usage limitations associated with the frequency of a navaid are modeled using sectors of circle. The same concept may apply for the Frequency class, which is associated with a service, and which is shown here for completeness. Radio Frequency Limitation feature is used to model all usages; service limitations as well as standard service coverage and extended coverage.

Point Reference Defines the location of a point using a combination of angles and distances from a significant point (navaid or from another designated point).

Segment Point Significant Points used for the definition of a route segment or terminal procedure are first modeled as "SegmentPoints". This enables the association with an optional PointReference and the specification of attributes that are common to both en-route points and terminal points.

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